This invention relates to an electrode assembly on a matrix type liquid crystal display panel, and more particularly it relates to a liquid crystal display panel with increased yield of manufacture.
In recent years, a substantial amount of effort in the field of liquid crystal matrix displays has been devoted to providing a high-density multi-line display, aiming at an improvement in image quality. Liquid crystal displays with matrix shaped electrode structures are quite favorable in fulfilling a power saving demand because of their capability of being excited with low power consumption.
A conventional drive technique for such a matrix type liquid crystal display, for example, the line sequential drive method as shown in FIG. 1, has long been known. A main memory 1 stores characters, symbols, patterns or the like and an intelligence signal converter 2 converts data contained in the memory 1 into the associated display patters. After those patterns are stored line by line into a buffer memory in a column driver 3, respective column electrodes Y.sub.1, Y.sub.2, . . . Y.sub.n are supplied with those patterns. Row electrodes X.sub.1, X.sub.2, . . . X.sub.m crossing the column electrodes, on the other hand, are sequentially enabled through a row driver 4, thereby displaying information contained in the buffer memory in a line-by-line fashion. A control 5 provides an operation control for the row and column driver circuits. A liquid crystal display with a matrix type electrode structure is labeled 6.
For the matrix type liquid crystal display panel, the greater the number of the rows (scanning the number) the higher the density and accuracy of display. However, with an increase in the number of the rows, the length of time at which a signal is applied per column, i.e., duty factor, is shortened and the problem of crosstalking arises. In particular, liquid crystal display panels show dull threshold characteristics and slow response characteristics, making it difficult to assure a satisfactory contrast. There are several ways to attempt to overcome this problem.
(1) The development of liquid crystal material having more definite threshold properties;
(2) A matrix address scheme in the optimum condition with an extended operating margin (.alpha.=V.sub.on /V.sub.off); and
(3) The design of an electrode structure with a seemingly higher resolution.
Though the first two ways (1) and (2) do not require modifications in the well known structure of liquid crystal cells, it appears almost impossible to increase drastically the number of excitable lines from the viewpoint of the present-day progress of liquid crystal materials, etc. Contrarily, the problem with the last method (3) is that the liquid crystal cells are sophisticated in construction but, it is actually possible to increase the number of excitable lines by a factor of two or more.
Typical ways of making possible the last approach (3) are as follows:
(a) double electrode structure PA1 (b) vertical partition, and PA1 (c) two-layered structure.
These methods may be adopted alone or in combination for achieving the intended purpose. Such a combination has been proposed by co-pending application Ser. No. 921,062 June 30, 1978, MATRIX TYPE LIQUID CRYSTAL DISPLAY PANEL by F. Funada et al, now U.S. Pat. No. 4,231,640.
Conventional electrode assemblies of matrix type liquid crystal display panels are shown in FIGS. 2 and 3, in which FIG. 2 shows a bare vertical partition and a combined vertical pertition and two-layered structure and FIG. 3 shows a combined vertical partition and double electrode and a combined vertical partition, double electrode and two-layered structure. This sort of electrode assembly as seen in FIGS. 2 and 3 is designed such that the distance l.sub.x between a particular scanning electrode X.sub.m and an adjoining scanning electrode X.sub.m+1 in a horizontal line each for defining a respective one of picture elements is equal to that l.sub.y between a particular upper block signal electrode Y'.sub.j and a lower block signal electrode Y.sub.j in a vertical direction. It is however very difficult to align both of those electrodes in an exact positioned relationship as seen in FIGS. 2 and 3 because of very narrow widths and distances of the respective electrodes in fixing relative positions between an electrode support carrying all of the scanning electrodes and another electrode support carrying all of the signal electrodes during manufacture of display panels.
For example, in the event that the edges 11 and 12 of the scanning electrodes X.sub.m+1 along its widths thereof are in disalignment with respect to lowest edge 21 of the upper block signal electrode Y.sub.j, and the upper edge of the lower signal block electrode Y.sub.j as shown in FIG. 4 or 6, hatched areas 13 and 23 where the electrodes do not overlap are of no use as part of a display panel at all.
Should the display panel with such disaligned electrodes be excited for display operation, the distance l.sub.3 between picture elements 101 and 102 corresponding to X.sub.m and X.sub.m+1 becomes greater than that l.sub.1 between picture elements 100 and 101 corresponding to the scanning electrodes X.sub.m-1 and X.sub.m as viewed from FIG. 5 or 7. The display screen is divided into an upper block and a lower block, thus deteriorating image quality of the display screen.
The conventional method therefore has the problem of decreased yield of manufacture because it requires exact alignment between the edges of the scanning electrodes and those of the signal electrodes.